Saxo Grammaticus, which was also the source material for Shakespeare's epic drama Hamlet.
In Royal Deceit (a really terrible title), the set-up is much the same as Hamlet--the young prince of Denmark has seemingly gone mad following the murder of his father (and in this case, brother as well).
Although the murder is blamed on two "scouundrels," the real murderer is the king's jealous brother (Gabriel Byrne), who co-opts the queen (Helen Mirren, looking luminously ageless). From the moment the uncle "modestly" accepts the crown in Amled's place, the story begins to diverge from the one we know, although elements remains--like the characters who became Rosencrantz and Guildenstern and the girl who was the model for Ophelia, here called Ethel (long E, pronounced EEE-thul), and played by a very young Kate Beckinsale. (She mostly wears shapeless costumes that make her look pudgy, which is unfortunate.)
Other people who show up in the movie, which came out in 1994, are Brian Cox as a sympathetic nobleman and Andy Serkis in a small role. (The actor playing one of Byrne's henchmen looks a lot like Chris Hemsworth of Thor and The Avengers.)
The movie is not really very good. The production value is about what you'd expect from a History Channel documentary. ("Let us give my brother a funeral fire fit for a king," the faithless uncle shouts and we cut to a pile of kindling fueling the lamest bonfire ever put on film.)
Oddly (and a choice that also reminds us of a History Channel documentary), most of the story is narrated, told to us by Oliver Fox. Perhaps the thought was that this would make the tale seem more like the stories told by skalds to entertain the nobility.
Mostly the movie alternates between melodrama and a downbeat sort of realism more appropriate to a kitchen-sink drama than an historical epic.
Fans of Bale might find the movie (which is streaming on Netflix right now) an interesting hour and a half of entertainment. (There's also a scene of Helen Mirren bathing topless with her maidens, flagellating themselves with tree branches that might have a certain appeal.)